[4] His paternal grandparents were Jacob Lockman and Catherine (née Paul) Lockman, and his maternal grandparents were Thomas H. Kennedy, an intimate friend of Scottish poet Robert Burns, and Margaret Kennedy, both of whom were born in Scotland.

[5][6] Lockman, who served in the old Volunteer Fire Department of New York City for seven years, was a law student when the U.S. Civil War broke out.

Lockman was again promoted to lieutenant colonel of the 119th New York Volunteer Infantry and fought in the Army of the Potomac under multiple Union Army Generals, including General George B. McClellan, Ambrose Burnside, Joseph Hooker and George G.

"[7] Lockman also participated in the Battles of Cassville, Pine Hill, Kolb's Farm, Dallas, Kennesaw Mountain, Peachtree Creek and the Siege of Atlanta.

[11] Together, Harriett and John were the parents of five children, three daughters and two sons, including:[1] He served as a vestryman of Trinity Church, a trustee of the New York Protestant Episcopal Public School, and a member of the New-York Historical Society, the St. Andrew's Society, the Metropolitan Club, the Church Club, the Army and Navy Club, the Metropolitan Museum of Art and the American Museum of Natural History.